SUMMARY The global burden of mental illness, including autism spectrum disorders (ASD), intellectual disability, epilepsy, Tourette disorder, schizophrenia and bipolar disorder, is enormous, whether measured in health care expenditures, lost productivity, or personal suffering. Unfortunately, there is a striking lack of insight into the underlying molecular biology of these syndromes. However, recent advances in gene discovery are setting the stage for a transformation in the understanding of these psychiatric disorders. Understanding pathobiology and developing novel treatments is becoming increasingly dependent on knowledge of biological networks of multiple types, including physical interactions among proteins and syntheticlethal and epistatic interactions among genes. Here we seek support for a new effort, the Psychiatric Cell Map Initiative (PCMI, www.pcmi.ucsf.edu), aimed at comprehensively understanding these complex interactions in psychiatric disorders and how they differ between diseased and healthy states. While we will focus on ASD in this proposal, this work will establish a paradigm to investigate other psychiatric disorders in future work. The PCMI is a multicampus initiative of the University of California, involving UC San Francisco, UC San Diego and UC Berkeley, which leverages genomics, proteomics, highthroughput sequencing, advanced network mapping, computational analysis, and research platforms developed by multiple PCMI investigators over the past decade. Thus primed, these platforms will be tuned to efficiently generate, assemble, and analyze molecular networks linked to ASD, in relevant cell types, with a view towards pathway and networkbased personalized therapy. Specifically, over the next five years the PCMI will seek to catalyze major phase transitions in ASD research and therapy by (1) Comprehensively mapping the networks of physical interactions among proteins linked to ASD, revealing the protein complexes and higherorder molecular units underlying ASD in multiple cell types of the human brain? (2) Mapping the parallel networks of syntheticlethal and epistatic interactions among ASD genes using CRISPRbased approaches? (3) Establishing the robust computational methodology, enduser software, and databases for assembly and use of ASD cell network maps in both basic and clinical modalities? (4) Translating molecular insights into an understanding of higher order phenotypes? (5) Building a critical mass of leading investigators focused on psychiatric disorders worldwide to expand PCMI into a global coordinated partnership? and (6) Training the current and nextgeneration of scientists in Network Biology and its applications to research focused on psychiatric disorders.